1. Field of the Invention
The present invention relates to a solution treatment unit for a substrate.
2. Description of the Related Art
In a photolithography process in semiconductor device fabrication processes, for example, resist coating treatment for coating the surface of a wafer with a resist solution to form a resist film on the wafer, exposure processing for exposing the wafer in a pattern, developing treatment for developing the exposed wafer, and the like are performed in sequence to form a predetermined circuit pattern on the wafer.
A developing treatment unit in which the aforementioned developing treatment is performed includes, for example, a developing solution supply nozzle for supplying a developing solution to the wafer, a spin chuck capable of rotating the wafer while holding it, a cup surrounding the outer periphery of the wafer, and the like. The developing treatment is carried out in such a manner that after the developing solution is supplied to the wafer held by the spin chuck and the wafer is developed in stationary condition for a predetermined period of time, the wafer is cleaned and dried while being rotated.
In the developing treatment, it is necessary to drain the developing solution and the like falling from the wafer and scatted from the wafer and to exhaust impurities floating in the developing treatment unit. Therefore, a drain pipe connected to a fan or the like on the factory side is provided in the lower portion of the cup, and conventionally drainage of the developing solution and the like and an atmosphere including impurities are collectively let out from the drain pipe.
However, if the drain of the developing solution and the like and the exhaust of impurities and the like are performed collectively by the drain pipe as described above, pressure loss occurs to the fan on the factory side which generates suction force of the drain pipe, and hence to maintain a predetermined exhaust quantity, it is necessary to rotate the fan at higher speed than usual. If the fan is maintained at high-speed rotation as described above, the power consumption increases correspondingly, and total running costs of the developing treatment increase. Moreover, the possibility that moist exhausted atmosphere comes in contact with the fan becomes higher, and hence corrosion and the like may occur to the fan.